De nouvelles mesures des taux de reaction de 17 O(p, α) 14 N et de 17 O(p, γ) 18 F sont presentee... more De nouvelles mesures des taux de reaction de 17 O(p, α) 14 N et de 17 O(p, γ) 18 F sont presentees. Ces resultats sont utilises pour etudier les abondances en oxygene isotopique dans les geantes rouges de forte masse (15 M ○. ) et de masse intermediaire (2 M ○. ).
In this work the evolution of the light elements in the Galaxy is investigated in the framework o... more In this work the evolution of the light elements in the Galaxy is investigated in the framework of consistent models for the solar neighborhood and the galactic disk. The following points are made: 1‐ It is shown, as already suggested in (19), that a consistent model of the solar neighborhood (Figs. 1 to 3) fails to explain the observed primary behavior of Be vs Fe if Be is produced as a secondary element, as usually assumed. Such a problem is already identified in the halo (for Be, and B), where it can be marginally solved by various, more or less plausible, assumptions. The difficulties encountered (independently) in both the halo and the disk can be ‘‘naturally’’ solved with the assumption that Be and B are produced as primary elements during the whole galactic evolution. The advantages and problems of a recently proposed site for such a primary production are presented. 2‐ The abundance gradients of D and 3He in the disk are evaluated in the framework of a model that reproduces most of disk properties...
Observed large scatters in abundances of neutron-capture elements in metal-poor stars suggest tha... more Observed large scatters in abundances of neutron-capture elements in metal-poor stars suggest that they are enriched a single or a few supernovae. Comparing predictions by an inhomogeneous chemical evolution model and new observational results with Subaru HDS, we attempt to constrain the origins of r-process elements.
The evolution of the C and O isotopes in our Galaxy is studied, on the basis of recent results of... more The evolution of the C and O isotopes in our Galaxy is studied, on the basis of recent results of stellar nucleosynthesis and recent models for the chemical evolution of the galactic disk. It is found that has a mixed primary and secondary origin, the former presumably from hot-bottom burning or from some other mechanism mixing protons with ^12^C synthesized in the star itself; both mechanisms may take place in intermediate mass stars. is of purely secondary origin and is produced in stars of all masses; its yields given by various authors are overestimated, probably because of the use of low (p,α) and (p,γ) rates. The ^18^O "puzzle" is quantitatively investigated and several solutions are considered, like the possibility of the solar system to have been formed in an OB association. The possibility of an error in the measured ^18^O abundance alone, either in the interstellar medium or in the solar system, is also considered and shown to offer a simple solution to that puzzle.
The r-Process: The Astrophysical Origin of the Heavy Elements and Related Rare Isotope Accelerator Physics - Proceedings of the First Argonne/MSU/JINA/INT RIA Workshop, 2004
... 1991, A&A, 252, 689 . 1993, in Origin and Evolution of the Elements, ed. N. Prantzos, E. ... more ... 1991, A&A, 252, 689 . 1993, in Origin and Evolution of the Elements, ed. N. Prantzos, E. Vangioni-Flam, & M. Cassé(Cambridge: Cambridge Univ. Press), in press Steigman, G., & Walker, T. 1992, Api, 385, L13 Soutoul, A., & Ferrando, P. 1989, in AlP Conf. Proc. No. ...
Monthly Notices of the Royal Astronomical Society, 2003
Based on the results of recent surveys, we have constructed a relatively homogeneous set of obser... more Based on the results of recent surveys, we have constructed a relatively homogeneous set of observational data concerning the chemical and photometric properties of Low Surface Brightness galaxies (LSBs). We have compared the properties of this data set with the predictions of models of the chemical and spectrophotometric evolution of LSBs. The basic idea behind the models, i.e. that LSBs are similar to 'classical' High Surface Brightness spirals except for a larger angular momentum, is found to be consistent with the results of their comparison with these data. However, some observed properties of the LSBs (e.g. their colours, and specifically the existence of red LSBs) as well as the large scatter in these properties, cannot be reproduced by the simplest models with smoothly evolving star formation rates over time. We argue that the addition of bursts and/or truncations in the star formation rate histories can alleviate that discrepancy.
... In that way, data from at least a dozen space missions (Apollo, ASCA, COBE, Exosat, Galileo, ... more ... In that way, data from at least a dozen space missions (Apollo, ASCA, COBE, Exosat, Galileo, Hipparcos, HST, ISO, ISEE-3, ORFEUS, ROSAT ... G. Nusser Jiang, M. Preen, D. Taylor, and S. Wenger, for the local organization of this workshop, and U. Pfander and X. Schneider for ...
Proceedings of The International Astronomical Union, 1998
The detection of the relatively short-lived (~106 years) radioactive Al-26 in our Galaxy, more th... more The detection of the relatively short-lived (~106 years) radioactive Al-26 in our Galaxy, more than 12 years ago, convincingly showed that nucleosynthesis is still active today on a large scale. The recent observations of the COMPTEL instrument aboard the Compton Gamma-Ray Observatory allowed for the first time to establish a map of the distribution of Al-26 in the Galaxy, suggesting that massive stars are its most probable sources. Future observations with the INTEGRAL satellite are expected to reveal details of that map, corresponding to major sites of current large-scale nucleosynthetic activity in the Galaxy. I will review these recent observations and discuss their astrophysical implications.
De nouvelles mesures des taux de reaction de 17 O(p, α) 14 N et de 17 O(p, γ) 18 F sont presentee... more De nouvelles mesures des taux de reaction de 17 O(p, α) 14 N et de 17 O(p, γ) 18 F sont presentees. Ces resultats sont utilises pour etudier les abondances en oxygene isotopique dans les geantes rouges de forte masse (15 M ○. ) et de masse intermediaire (2 M ○. ).
In this work the evolution of the light elements in the Galaxy is investigated in the framework o... more In this work the evolution of the light elements in the Galaxy is investigated in the framework of consistent models for the solar neighborhood and the galactic disk. The following points are made: 1‐ It is shown, as already suggested in (19), that a consistent model of the solar neighborhood (Figs. 1 to 3) fails to explain the observed primary behavior of Be vs Fe if Be is produced as a secondary element, as usually assumed. Such a problem is already identified in the halo (for Be, and B), where it can be marginally solved by various, more or less plausible, assumptions. The difficulties encountered (independently) in both the halo and the disk can be ‘‘naturally’’ solved with the assumption that Be and B are produced as primary elements during the whole galactic evolution. The advantages and problems of a recently proposed site for such a primary production are presented. 2‐ The abundance gradients of D and 3He in the disk are evaluated in the framework of a model that reproduces most of disk properties...
Observed large scatters in abundances of neutron-capture elements in metal-poor stars suggest tha... more Observed large scatters in abundances of neutron-capture elements in metal-poor stars suggest that they are enriched a single or a few supernovae. Comparing predictions by an inhomogeneous chemical evolution model and new observational results with Subaru HDS, we attempt to constrain the origins of r-process elements.
The evolution of the C and O isotopes in our Galaxy is studied, on the basis of recent results of... more The evolution of the C and O isotopes in our Galaxy is studied, on the basis of recent results of stellar nucleosynthesis and recent models for the chemical evolution of the galactic disk. It is found that has a mixed primary and secondary origin, the former presumably from hot-bottom burning or from some other mechanism mixing protons with ^12^C synthesized in the star itself; both mechanisms may take place in intermediate mass stars. is of purely secondary origin and is produced in stars of all masses; its yields given by various authors are overestimated, probably because of the use of low (p,α) and (p,γ) rates. The ^18^O "puzzle" is quantitatively investigated and several solutions are considered, like the possibility of the solar system to have been formed in an OB association. The possibility of an error in the measured ^18^O abundance alone, either in the interstellar medium or in the solar system, is also considered and shown to offer a simple solution to that puzzle.
The r-Process: The Astrophysical Origin of the Heavy Elements and Related Rare Isotope Accelerator Physics - Proceedings of the First Argonne/MSU/JINA/INT RIA Workshop, 2004
... 1991, A&A, 252, 689 . 1993, in Origin and Evolution of the Elements, ed. N. Prantzos, E. ... more ... 1991, A&A, 252, 689 . 1993, in Origin and Evolution of the Elements, ed. N. Prantzos, E. Vangioni-Flam, & M. Cassé(Cambridge: Cambridge Univ. Press), in press Steigman, G., & Walker, T. 1992, Api, 385, L13 Soutoul, A., & Ferrando, P. 1989, in AlP Conf. Proc. No. ...
Monthly Notices of the Royal Astronomical Society, 2003
Based on the results of recent surveys, we have constructed a relatively homogeneous set of obser... more Based on the results of recent surveys, we have constructed a relatively homogeneous set of observational data concerning the chemical and photometric properties of Low Surface Brightness galaxies (LSBs). We have compared the properties of this data set with the predictions of models of the chemical and spectrophotometric evolution of LSBs. The basic idea behind the models, i.e. that LSBs are similar to 'classical' High Surface Brightness spirals except for a larger angular momentum, is found to be consistent with the results of their comparison with these data. However, some observed properties of the LSBs (e.g. their colours, and specifically the existence of red LSBs) as well as the large scatter in these properties, cannot be reproduced by the simplest models with smoothly evolving star formation rates over time. We argue that the addition of bursts and/or truncations in the star formation rate histories can alleviate that discrepancy.
... In that way, data from at least a dozen space missions (Apollo, ASCA, COBE, Exosat, Galileo, ... more ... In that way, data from at least a dozen space missions (Apollo, ASCA, COBE, Exosat, Galileo, Hipparcos, HST, ISO, ISEE-3, ORFEUS, ROSAT ... G. Nusser Jiang, M. Preen, D. Taylor, and S. Wenger, for the local organization of this workshop, and U. Pfander and X. Schneider for ...
Proceedings of The International Astronomical Union, 1998
The detection of the relatively short-lived (~106 years) radioactive Al-26 in our Galaxy, more th... more The detection of the relatively short-lived (~106 years) radioactive Al-26 in our Galaxy, more than 12 years ago, convincingly showed that nucleosynthesis is still active today on a large scale. The recent observations of the COMPTEL instrument aboard the Compton Gamma-Ray Observatory allowed for the first time to establish a map of the distribution of Al-26 in the Galaxy, suggesting that massive stars are its most probable sources. Future observations with the INTEGRAL satellite are expected to reveal details of that map, corresponding to major sites of current large-scale nucleosynthetic activity in the Galaxy. I will review these recent observations and discuss their astrophysical implications.
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Papers by N. Prantzos